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At least 19 recordsLinked to original sources
PubMed1979

Structure and formation of ankylosis in Xenopus laevis.

The structure of ankylotic teeth in Xenopus laevis was studied by light, transmission, and scanning electron microscopy as well as by microradiography in decalcified and undecalcified specimens. The mature teeth of Xenopus laevis are calcified from the crown to the base, fused to the jaw bone, and have no uncalcified area, such as a fibrous ring separating the tooth into the crown and pedicle. Microradiography shows that the mature tooth and jaw bone appear as an X-ray opaque area, except for the basal region of the dentine. This region is composed of an X-ray translucent area and an X-ray opaque thin layer on the lingual side of the translucent area. The mature tooth is composed of two differently calcified areas: (1) a highly calcified area, which makes up almost all of the tooth and contains a thin layer of the basal dentine on the lingual side, and (2) a lowly calcified basal dentine, which is fused to the jaw bone. Therefore, the lowly calcified area does not completely separate the dentine and jaw bone. Repeating banding patterns among the collagen fibrils differ among the dentine-forming area and the matrices of dentine and jaw bone. During the formation of ankylosis of the tooth germ, collagen bundles in the dentine-forming area accumulate directly on the surface of the jaw bone. Consequently, the mature teeth of Xenopus laevis fuse to the jaw bone directly without the mediation of the other structures.

Animals↗
PubMed1978

Incorporation of tetracycline into impeded and unimpeded mandibular incisors of the mouse.

Twenty-four hours after a tetracycline injection, the unimpeded, and more rapidly erupting, mouse mandibular incisor contained 20% to 44% more tetracycline than the contralateral, uncut incisor. It was concluded that the increased tetracycline incorporation reflected a higher rate of mineralization associated with faster tooth formation in the unimpeded tooth. By measuring the amount of tetracycline which became incorporated at different times after an incisor was shortened, it was possible to investigate an early stage of the response of the incisor to cutting. A significant increase in the capacity of the tooth to incorporate tetracycline was detectable 4 h after shortening the tooth, and this was maximal after another 4 h.

Animals↗
PubMed1991

[The adjustment of the canine teeth adjacent to the cleft depending on the time of late primary osteoplasty].

Timing for secondary bone-grafting is decisive for a successful orthodontic alignment of canines, adjacent to the cleft. This could be shown after evaluation of diagnostic data from 123 patients with unilateral cleft alveolus and cleft lip and palate and in a clinical follow-up of 29 former patients, 7.3 year after treatment. Concerning eruption and periodontal conditions of cleft adjacent canines, better results could always be seen, if bone was grafted, before mineralisation of canine root has reached 3/4 of its total length. If grafting was done after this stage, disturbances in eruption occurred more frequently. Most canines tended to erupt palatally but could successfully be aligned orthodontically. The follow-up study showed good results concerning probing depth, pulp reaction and periodontal stability. Using our own clinical data, best chronologic age for bone grafting lies between 9 1/2 and ten years.

Bone Transplantation↗
PubMed1975

[Transfer of 45Ca during amelogenesis studied by autoradiography and electron microscopy].

45Ca transfer through the stratum intermedium and the secreting ameloblasts towards enamel has been studied by quantitative electron microscopical autoradiography in tooth-germs of newborn cats following intravenous injection of the isotope. Two transfer pathways were demonstrated. The relatively more important direct path passed through the stratum intermedium and ameloblast intercellular spaces and reached the enamel directly. The second pathway consisted in an intracellular transfer through the ameloblasts. 45Ca penetrated the cell through its basal pole. The mitochondria were the most highly labeled organelles at the different experimental time intervals studied. A maximum of radioactivity was respectively noticed at 30 min and 1 h in the endoplasmic reticulum and the Golgi apparatus. A total absence of silver grains was noted over the secretory ameloblastic bodies. At 6 h, the highest labeling was observed over enamel and especailly over the inner enamel along the enameldentin junction.

Ameloblasts↗
PubMed1991

Amelogenin post-secretory processing during biomineralization in the postnatal mouse molar tooth.

The primary structures, molecular genetics and biosynthesis of the amelogenin protein of the developing tooth are established, but knowledge of their subsequent post-secretory processing and its relation to enamel biomineralization is fragmentary. Preparations of tooth matrix proteins were isolated from molars (M1) of mice from birth to 15 days and analysed by SDS-PAGE and immunochemical methods. Amelogenin proteins, isolated and partially purified by HPLC, were characterized by amino acid analysis and SDS-PAGE. At birth a 26 kDa amelogenin was present that during subsequent developmental stages generated a series of 20-25 kDa amelogenins differing in apparent size by approximately 1 kDa. Amino acid analyses showed that all these amelogenins have amino-terminal TRAP sequences; analyses for both glycosylation and phosphorylation were negative. It is suggested that these post-secretory amelogenins are generated by a sequence of specific carboxy-terminal cleavages, and that the observed post-secretory processing of amelogenin is functionally linked to the structure of the enamel matrix and the control of crystallite development.

Age Factors↗
PubMed1979

Deciduous teeth contain histories of developmental disturbances.

The crowns of the deciduous teeth are permanent structures which form by incremental growth during the second half of pregnancy and first year of life. These structures become available between the ages of 6 and 12 years with normal exfoliation and can then be studied histologically to demonstrate evidence of metabolic disturbances occurring during tooth development. As the chronology of disturbances can be assessed with reasonable accuracy, such studies provide a potentially valuable research tool.

Female↗
PubMed1992

An example of regional variation in the tempos of tooth mineralization and hand-wrist ossification.

Two groups of adolescent orthodontic patients, one from the Midwest and one from the Midsouth, were compared to test the clinical impression that the permanent teeth of southern children form and erupt at significantly later ages. Indeed, a marked difference is documented, with the Midsouth series achieving mineralization stages at least 1 1/2 years later on average. This suggests that regional differences are appreciably greater than previously suspected. Clinical consequences revolve on the use of conventional (generally Northeast-based) norms for tooth formation and eruption and predictive models of facial growth. In contrast, the analysis of rates of hand-wrist development (bone age) of these same subjects disclosed no difference; this further confirms the essential independence of development of the dental and osseous tissue systems.

Adolescent↗
PubMed1977

Influence of different endodontic methods of treatment upon the process of apical closure of immature pulpless human teeth and the structure of the newly formed calcified tissue in apical opening.

A description is given of the pathohistological structure of the calcified tissue in the apical opening of four extracted immature pulpless human teeth treated by various endodontic methods. It is concluded that in the tooth treated by mortal extirpation there was neither histological healing nor any tendency for further apex formation. In both the tooth where vital extirpation was performed and in one of the teeth treated as apical periodontitis, the apices were formed from conglomerates of different calcified tissues, identical to the tissue which was formed under comparable conditions in experimental dogs. In the fourth human tooth also treated as apical periodontitis after treatment the apical opening closed with irregular dentine tissue. In this study consideration was given to the problem of the origin of the odontoblasts which co-exist with the hard destructive process present in some pulpless teeth. It is concluded that in the case presented in this study the irregular dentine was formed by the same odontoblasts which took part in the process of normal odontogenesis. This fact, should be respected in the course of endodontic treatment of immature pulpless teeth.

Animals↗
PubMed1976

A radiographic study of mineralization of permanent teeth in a group of children aged 3-7 years.

The purpose of the present study was, by using a standardized radiographic technique, to assess the time of selected mineralization stages of all permanent teeth except the second and third molars in a group of 580 children aged 3-7 years. A complete radiographic examination, consisting of nine intraoral films, was made of each child, using Eggen's film holder. According to degree, mineralization of the teeth was subdivided into nine stages. The cap relation between the two variables, mineralization stage and chronologic age, was calculated by linear regression analysis. The hypothesis of the present study, that linearity exists between the two variables, was confirmed within and close to the investigated age group.

Child↗
PubMed1976

Developmental disturbances in permanent teeth after intrusion of their primary predecessors.

The frequency and type of developmental disturbances in the permanent teeth in relation to the child's age at the time of injury were examined in 78 patients with 100 intruded primary incisors. The central incisors were found to be the most frequently affected teeth. Only maxillary teeth were involved. The dominating age group was 1-3 years and intrusion was seldom seen after the age of 4 years. The frequency of disturbed normal development of the permanent teeth was 54%. In eight cases the intruded teeth were removed immediately, 86 teeth reerupted, and six teeth did not reerupt. Internal white enamel hypoplasia was seen frequently; external hypoplasia, seldom.

Age Factors↗
PubMed1991

Light and transmission-electron microscopy study of enamel organ cells in germectomized human third mandibular molars.

Using nine serially sectioned germectomized mandibular third molars it was possible to examine light microscopical (LM) and transmission-electron microscopical (TEM) features of maturing human enamel organ cells. The degree of enamel mineralization was estimated by quantitative imbibition studies in polarized light. It was possible to distinguish between three progressive stages of enamel mineralization. The most advanced stage was characterized by external enamel porosity. In the least advanced stages the enamel porosity appeared more extensive beneath a less porous surface layer. Ruffle- and smooth-ended ameloblasts were identified corresponding to the maturing enamel. Smooth-ended ameloblasts were the most frequently observed. However, no preferences for one of the two cell types could be observed in relation to the different stages of enamel mineralization. The maturing human enamel organ cells broadly revealed the same characteristics with respect to morphology features, intracellular organization, and junctional complexes as described in the maturation zone of the rat incisor enamel organ. Our findings therefore add to the view that the basic pattern of amelogenesis is identical in human and rat incisor enamel.

Adolescent↗